If you open a can of chicken noodle soup and immediately examine it microscopically, you will find no microorganisms. If you let the open can sit on the shelf for a few weeks and then examine it, you will find lots of microorganisms. The origin of these microorganisms is most likely:

Airborne microorganisms

a

explanation:

the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.